A functional requirement defines what the system must do to meet the user’s needs. There are two types of functional requirements:
- Generic functional requirements: used to describe general principles, for example, to indicate that creating a duplicate client with the same email address should not be possible.
- Email-type functional requirements: used to specify the details of emails that may be sent by the system. For each requirement of this type, all the information necessary for sending the email is specified: the subject of the email, recipients, reply address, and message content.
For example, functional requirements define the basic services that the system must provide:
- « Authenticate the user each time they log in to the system »
- « System shutdown in case of a cyberattack »
